Financial market predictability with tensor decomposition and links forecast.

Inspecting financial markets from a complex network perspective means to extract relationships and interdependencies from stock price time series. Correlation networks have been shown to adequately capture such dependence structures between financial assets. Moreover, researchers have observed modifications in the correlation structure between stock prices in the face of a market turbulence. This happens because financial markets experience sudden regime shifts near phase transitions such as a financial crisis. These abrupt and irregular fluctuations from one state to another lead to an increase of the correlation between the units of the system, lowering the distances between the stocks in a correlation network. The aim of this paper is to predict such abrupt changes by inferring the forthcoming dynamic of stock prices through the prediction of future distances between them. By introducing a tensor decomposition technique to empirically extract complex relationships from prices' time series and using them in a portfolio maximization application, this work first illustrates that, near critical transitions, there exit spatial signals such as an increasing spatial correlation. Secondly using this information in a portfolio optimization context it shows the ability of the methodology in forecasting future stock prices through these spatial signals. The results demonstrate that an optimization approach aiming at minimizing the interconnectedness risk of a portfolio by maximizing the signals produced by tensor decomposition induces investment plans superior to simpler strategies. Trivially speaking portfolios made up of strongly connected assets are more vulnerable to shock events than portfolios of low interconnected assets since heavily connected assets, being close to a transition point, carry a significant amount of interconnectedness risk, i.e. tail events propagate more quickly to these assets.

Congenital toxoplasmosis: efficacy of maternal treatment with spiramycin alone.

PROBLEM: The evidence supporting an additional benefit of a combined regimen of pyrimethamine-sulfonamides compared with spiramycin alone in the secondary prevention of congenital toxoplasmosis was critically evaluated. METHOD OF STUDY: We reviewed the series of cases published in the English literature on antiparasitic treatment of acute toxoplasmosis infection in pregnancy, using spiramycin until fetal infection is documented, then using cycles of spiramycin alternated with combined pyrimethamine-sulfonamide therapy. We then compared the occurrence of overt disease among infected offspring (both severe, represented by ophthalmologic or cerebral abnormalities, and mild occurrences, represented by asymptomatic intracranial calcifications and retinal scars without visual impairment) between the published case series and our consecutive series of cases treated during a 10-year period (January 1986-December 1995) with spiramycin alone. RESULTS: The prevalence of fetal infection in our series was 7.8% (12/154), similar to that reported after alternated regimens (7.0%). The rate of overt disease among infected fetuses is not different after treatment with alternated regimens than after continuous antibiotic spiramycin therapy [23% (19/82) vs. 10% (1/10); relative risk, 2.3; 95% confidence interval, 0.4, 47.0]. The pharmacokinetics of the drugs used may account for this finding. CONCLUSION: The treatment of acute toxoplasmosis in pregnancy with an alternated antibiotic regimen of pyrimethamine-sulfonamide is not more efficacious at preventing overt neonatal disease than treatment with continuous spiramycin alone.

Results of a preventive program for congenital toxoplasmosis.

All pregnant women followed during the period 1982-87 were screened for toxoplasmosis, and 35 patients had documented seroconversion or doubtful toxoplasmosis titers. One patient opted for pregnancy termination. The remaining were followed with a protocol that included serial ultrasound examinations and prophylactic antibiotic treatment of the mother and neonate. No fetal abnormalities related to congenital toxoplasmosis were found. All the infants had negative toxoplasmosis test titers at birth; at follow-up only one was found to have developed a subclinical infection, at 2 months of age. Our data suggest that antiparasitic treatment during pregnancy for those at risk for Toxoplasma infection may reduce the transmission rate.